An organic electronic device is an electronic device using an organic semiconductor substance, and it is required in the organic electronic device that holes and/or electrons are interchanged with each other between an electrode and an organic semiconductor substance. The organic electronic device may be classified into two types according to the operational mechanism. One type is an electronic device in which an exciton is formed in an organic material layer by photons provided from an external light source to the device, and the exciton is divided into an electron and a hole, and then the electron and the hole are transported to respective electrodes to be used as a current source (voltage source). The other type is an electronic device in which a hole and/or an electron is injected into an organic semiconductor material layer forming an interface with an electrode by applying a voltage or current to two or more electrodes, so as to allow the device to operate by means of the injected electron and/or hole.
Examples of the organic electronic device include an organic light emitting device, an organic solar cell, an organic photoconducting (OPC) drum, and an organic transistor. All the above-mentioned examples of the organic electronic device require an electron/hole injecting material, an electron/hole extraction substance, an electron/hole transport substance, or a light emitting substance in order to drive the device. Hereinafter, the organic light emitting device will be described in detail but the electron/hole injecting material, the electron/hole extraction substance, the electron/hole transport substance, or the light emitting substance of the above-mentioned organic electronic device operate in a similar mechanism.
Generally, organic light emission means that electric energy is converted into light energy by using an organic substance. An organic light emitting device using the organic light emission typically includes an anode, a cathode, and an organic layer that is interposed between the anode and the cathode. The organic layer is to have a multilayered structure made of different substances in order to improve efficiency and stability of the organic light emitting device. For example, the organic layer may be formed of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. If voltage is applied to the electrodes in the organic light emitting device having the above-mentioned structure, a hole is injected into the organic material layer at an anode and an electron is injected into the organic material layer at a cathode. When the hole meets the electron, an exciton is generated, and light is generated when the exciton is converted into a bottom state. It is known that the organic light emitting device has properties such as self-light emission, high luminance, high efficiency, a low driving voltage, a wide viewing angle, high contrast, and a high-speed response.
The materials used for the organic material layer of the organic light emitting device may be classified into a light emitting material and a charge transporting material, for example, a hole injecting material, a hole transporting material, an electron transporting material, and an electron injecting material according to the type of function. The light emitting material may be classified into a blue, green, or red light emitting material and a yellow or orange light emitting material required to ensure a better natural color according to a light emitting color. Furthermore, a host/dopant system may be used as the light emitting material for the purpose of enhancing color purity and light emitting efficiency through energy transfer. This is based on a mechanism where if a dopant, which has better excellent light emitting efficiency and lower energy band interval than those of a host constituting the light emitting layer, is mixed with the light emitting layer in a small amount, an exciton that is generated from the light emitting layer is transported to the dopant to emit light at high efficiency. In this connection, since the wavelength of the host is moved toward the wavelength of the dopant, it is possible to obtain light having a desired wavelength according to the type of dopant.
In order to allow the organic light emitting device to fully exhibit the above-mentioned excellent characteristics, a material constituting the organic material layer in the device, for example, a hole injecting material, a hole transporting material, a light emitting material, an electron transporting material, and an electron injecting material should be essentially composed of a stable and efficient material. However, the development of a stable and efficient organic material layer material for the organic light emitting device has not yet been fully realized. Accordingly, the development of new materials is continuously desired. The development of such a material is equally required in the above-mentioned other organic electronic devices.